Induction heating furnaces



March 12, 1963 R. s. SEGSWORTH 3,031,391

INDUCTION HEATING FURNACES Filed Feb. 25, 1960 2 Sheets-Sheet 1 IIIIIIIIIIIIIAS 30 Z8 H7. 3.

34a INVENTOR.

ATTORNEYS March 12, 1963 R. s. SEGSWORTH 3,081,391

INBUCTION HEATING FURNACES Filed Feb. 25, 1960 2 Sheets-Sheet 2 2, 17 7 18 ,6. In. J

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United States Patent 50 7 3,081,391 INDUCTION HEATING FURNACE?) Robert Sidney Segsworth, Ewing Township, Mercer County, N.J., assignor to Ajax Magnethermic Corporation, Youngstown, Ohio, a corporation of Ohio Filed Feb. 25, 1960, Ser. No. 11,091 2 Claims. (Ci. 219-4049) This invention relates primarily to improvements in devices employing hollow current carrying conductor means which become heated in use and wherein cooling is effected by fluid flow therethrough. The invention relates more particularly to the provision of means in association.

with such fluid flow conductor means for protecting the conductor against over-heating and adapted to shut off flow of current to the conductor in response to a predetermined change in the rate of flow of such fluid and the invention has particular application for use in induction heating furnaces, billet heaters, frequency changing devices or like devices employing hollow induction coil means with fluid flowing in the said coil means.

It is an object of this invention to provide a device of the above type having means which provide protection against overheating of the device due to coolant failure.

It is also an object of this invention to provide an improved device of the type referred to wherein the protection means is responsive only to major changes in the flow of the fluid.

A still further object of this invention is to provide a device of the type referred to with protection means which will protect the device against unnecessary fluctuations in the flow of electrical current.

Yet another object of this invention is to provide such a device having protection means of the type related which is simpleand sturdy in construction and extremely reliable in operation.

Further objects of the invention and the invention itself will be readily understood from the following specification and the accompanying drawings, in which said drawings:

FIG. 1 is a semi-diagrammatic showing of an electrical induction heating furnace and the protection means therefor;

FIG. 2 is a perspective detail of a cup element associated with the protection means shown in FIG. 1;

FIG. 3 is a detail in partial section of a switch; and

FIGS. 4, 5 and 6 are sectional details of the protection means shown under a variety of operating conditions.

Referring now to the figures of the drawings, in all of which like parts are designated by like reference characters, in FIG. 1 there is shown, as an example of one application of this invention, an electrical induction heating [furnace 10 comprising a plurality of helically wound coils 11. The coils 11 preferably comprise a continuous, hollow conductor 9 wound about a cylindrical liner 10a having a longitudinal aperture 12 therethrough whereby material or objects to be heated are introduced into the furnace. The conductor 9 is provided at one end thereof with an intake portion 13 and at the other end thereof with an outlet portion 14. It will be understood that in cooling the furnace 10, a suitable fluid, such as water,

:from any suitable supply is introduced into the intake portion 13 and said fluid preferably flows successively through the contiguous coils 11 to be discharged at the opposite end of the furnace through the outlet portion 14.

- Fluid which is discharged from the outlet portion 14 of the conductor 9 is exhausted into an opened drain 15. Said drain is preferably provided with an enlarged, up-

wardly opened mouth portion 16 by means of which the fluid is directed into the open drain 15.

The protection means of my invention generally comprises a switch assembly, generally indicated at 20,

3,081,391 Patented Mar. 12, 1963 mounted on one side of the outer surface of the mouth portion 16 of the drain by means of an angled bracket 17 secured to the said mouth portion 16 in any suitable manner such as by a threaded bolt 18. The upper portion of the bracket 17 projects outwardly and obliquely upwardly as indicated at 17a. The switch assembly 20 is provided with a base 21 which is secured to the oblique portion 17a of the bracket 17 by means of a small bolt 22.

A switch 23 is mounted upon the upper surface of the base 21 and is provided with a laterally projecting, pivoted arm 24 which is preferably formed of light weight, flat, relatively rigid sheet metal pivoted between upstanding ears 25 projecting upwardly from the upper surface of the switch 23. A major portion of the arm 24 projects beyond the car 25 in the direction of the open mouth portion 16 of the drain 15 and a relatively shorter portion of said arm projects beyond said ears in the opposite direction, as indicated at 2411.

As best shown in FIG. 3, the switch 23 comprises a housing 23a having a wall 23b surrounding the switching mechanism. The uppermost portion of the wall 23b is apertured at 26a beneath the pivoted arm 24 and an upwardly projecting switch button 26 is seated therein, which button projects upwardly into contact'with the lower surface of the longer arm 24. The lowermost end of said switch button is disposed within the housing 23a and is provided with a circumferential, radially projecting flange 27 which abuts the inner surface of the upper portion of the wall 23b and limits the upward movement of said switch button. A pin 28 is secured within a downwardly open socket 28a of said switch button, said pin projecting downwardly through an aperture 28b of a small bracket 29. The bracket 29 is secured to a side portion of the wall 23b in any suitable manner and is disposed parallel with and spaced from the uppermost portion of said wall. A coil spring 30 is telescoped over the pin 28 and compressively disposed between the flange 27 and the bracket 29 whereby the switch button 26 and said pin are resiliently urged in an upward direction.

Downward movement of said switch button 26 is adapted to close a pair of contacts 31 and 32. The contact 31 is fixedly secured by a screw 31a adjacent one end of an irregularly formed mounting member 33 disposed within the housing 23a. A portion of said fixed contact projects through the adjacent side portion of the wall 23b to form the terminal 47 whereby said fixed contact is connected to the line 45.

The movable contact 32 is secured to the distal end of a cantilevered, flat spring conductor 34 which is electrically connected to the terminal 46 as indicated at 34a. The conductor 34 resiliently urges the contact 32 in an upward direction away from the fixed contact 31, and the pin 23 is adapted to pivot said movable contact toward said fixed contact. The lowermost end of said pin is disposed above the spring conductor 34 adjacent the proxirnal end of said conductor whereby depression of the switch button 26 causes said conductor to pivot downwardly. The contacts 31 and 32 are thereby closed and electrical current through the switch is maintained.

The spring 30 biases the switch button 26 upwardly with sufficient force to maintain the arm 24 in a slightly upwardly pivoted position to allow the switch 23 to open in the absence of other forces.

Referring now to FIGS. 1 and 2, the distal end of the switch arm 24 provides support means for a cup 55. The cup 55 comprises an upwardly open, generally rectangu lar container having flat side wall portions 55a and flat end wall portions 55b. One of the end walls 55b is provided with an obliquely upwardly projecting lip 550 by means of which the cup 55 is mounted to the distal end of the arm 24. The arm 24 and the lip 55c are preferably welded, brazed or otherwise suitably secured tocause damage to the coils or liner of the furnace.

gether in flatwise, over-lapping contact as best shown in FIG. 1.

The cup 55 is also provided with a'flat bottom wall 55d which is apertured at 56. The cup 55 is so mounted to the end of the arm 24 by means of the lip 550 that said cup is disposedto receive the stream of water or other coolant which is normally continuously being discharged through the outlet portion 14. Fluid so entering the cup 55 normally maintains the cup substantially full and the weight thereof causes the arm 24 to move downwardly, the switch button 26 to be depressed, and the switch 23 to be maintained in closed position.

The cup 55 and the arm 24 are of such combined weight that when said cup is empty, the arm 24 is maintained in its upwardly pivoted position and said cup is elevated by saidarrn to the position as shown in FIG. 6. The switch 23 is then open.

As the cup 55 is filled with the coolant, said cupbecomes progressively heavier until the weight thereof causes the arm 24 to press downwardly upon the switch button 26 with suflicient force to overcome the bias of the spring 30. When this happens, the switch 23 is caused to close. If the coolant is not continually added to that which is already in said cup, loss of coolant through the aperture 56 so lightens said cup that the arm 24 moves upwardly and the switch 23 again opens.

The critical fluid level at which the switch 23 closes is substantially less than completely full. For example, a critical level of 90 percent in a cup of the size and dimension as shown in FIG. 2 has been found to be excellent whereby as long as the rate of flow of the discharging coolant is suflicient to maintain the cup 90 percent full or more, the switch 23 is closed, and when the rate of flow is insuflicient to maintain such level, said switch opens. Y

Electrical current for the furnace 10 is provided as for ergy is hence provided to the coils 11 whereby the induc tion heating furnace operates according towell known induction heating principles.

A switch 42 is interposed in the lead 41 for interruption of current to the furnace. Said switch 42 is normally biased into open position by a spring 42a and is closed by means of a solenoid 43. When the solenoid 43 is energized, the switch 42 encloses, and when said solenoid is de-energized, the switch 42 returns to its normally open condition.

The solenoid 43 is adapted to be energized through lines 44 and 45. The switch 23 is interposed in the line 45 and connected thereto by the terminals 46 and 47. It will be understood that the switch 23 is connected to any suitable source of electrical energy through lines 44 and 45 whereby the operation of said switch energizes or deenergizes the solenoid 43.

In induction heating furnaces or similar devices of the type herein referred to, it is necessary that a suitable cooling fluid, such as water, flow substantially continuously through the hollow conductor 9 which forms the coils 11 whereby sufficient heat is carried off to prevent overheating of the furnace. When a coolant such as water is used, the rate of flow of the fluid is subject to variation due to changes in available water pressure. These changes in pressure are generally minor in nature, but occasionally the rate of flow may drop for a length of time suflicient to The furnace as herein disclosed and described is adequately protected against substantial and enduring changes in the rate of water flow or complete failure thereof by means As shown in FIG. 4, the water is normally discharged from the furnace coils at a rate which is more than suflicient to maintain the cup 55 full of water. A certain amount of the excess water flows out of the cup 55 through the aperture 56, and the remainder spills over the sides of the cup and into the drain 15. The weight of the cup 55 under these conditions is sufflcient to hold the arm 24 and the switch button 26 in a depressed position whereby the switch 23 is held closed and the solenoid 43 is energized. The switch 42 in the lead 41 will then be maintained in a closed position against the spring 42a and the current will be supplied to the furnace 10.

i As best seen in FIG. 6, if the supply of coolant fails completely, the cup 55 empties itself through the aperture 56 in the bottom wall 55d, and the weight of the empty cup is such that the arm 24 will, be pushed upwardly by the switch button 26. When the switch button 26 attains the position shown in- FIG. 6, the swi-tch23 opens, tie-energizing the'solenoid 43 and opening the switch 42. Current through the conductors 9 is thereby cut off and overheating of said furnace is obviated.

If the rate of flow of the fluid has been reduced but not completely stopped, the cup 55 may be maintained in only partially filled condition. As illustrated in FIG. 5, under such condition the amount of fluid flowing into the cup closely approximates that which is being lost through the aperture 56. The cup 55 is still sufliciently heavy because of its water content to maintain the switch 23 in its closed position whereby the solenoid 43 remains energized.

The point :at which the cup 55 will be light enough to release the switch 23 will depend upon the relationship between the strength of the spring 30, the size of the cup 55, and the size of the aperture 56 in the bottom of said cup. It is undesirable to have the current to the furnace cut off in response to minor changes in the flow of the water since this is not necessary to the full protection of the furnace and interferes with the proper functioning of the furnace. Even substantial changes in the rate of flow are not harmful and will not result in overheating of the furnace if said changes are momentary or of very short duration. For that reason, the cup 55 in the present invention is so designed in size and so apertured at the bot-' tom thereof that it will maintain the switch 23 in its closed position when the fluid therein is substantially less than the amount necessary to fill the cup. In this way a time delay is provided between an instant when the rate of flow of the fluid is reduced and the point at which the switch 42 in the lead 41 is opened.

Under normal conditions wherein a norm-a1 rate of flow is provided through the coil 11 of the furnace, the cup 55 will be maintained full to the point of overflowing as illustrated in FIG. 4. A slight reduction in the rate of flow will still maintain the cup 55 full of water since the amount I which enters the cup will be as great as that which is being lost through the aperture 56. If there is a substantial reduction in the rate of flow, the cup 55 will still maintain the switch 23 in its closed position until said cup'has partially emptied itself. This would result when either the flow of fluid is cut off altogether or when the amount being exhausted into the cup is something less than that being discharged therefrom through the aperture 56. Thus it will be seen that the furnace 10 will remain energized not only when the rate of flow of the fluid is normal but also during moderate fluctuations or temporary interruptions in the flow which are of no immediate I danger to the furnace itself.

If the flow of coolant which is discharged from the furnace is very large, only a portion of said coolant may be diverted for the purpose of actuating the switch 23. By this means it is possible to use a much smaller switch and cup assembly than would be necessary if the flow were much greater.

It will be understood that many departures from the details of this invention as herein described and illustrated may be made without, however, departing from the spirit thereof or the scope of the appended claims.

What I claim is:

1. An electrical induction heating furnace comprising a continuous, helically wound, hollow conductor, a fiuid coolant flowing through said conductor and being discharged therefrom into an open drain, switch means mounted adjacent said drain and having an operative member projecting over said drain, said switch means actuable to cut oif the current to said furnace in response to movement of said operative member, a container having an aperture in the bottom thereof mounted to the end of said operative member whereby a stream of coolant being discharged from said conductor is directed into said container, said switch means having resilient means whereby it is biased into an actuated position to cut off the current to said furnace, the weight of said container when partially full of coolant being suflicient to depress said operative member and deactivate said switch means, said aperture allowing escape of coolant from said container whereby when the rate of flow of said stream drops and remains below that which is necessary to cool said furnace, said container progressively lightens to the point where said resilient means overcome the weight of said container and said switch means is activated to cut off the cur-rent to said furnace.

2. An electrically operated device of the type referred to comprising a continuous helically wound, hollow conductor, a fluid coolant flowing through said conductor and being discharged therefrom into an open drain, switch means mounted adjacent said drain and having an operative member projecting over said drain, said switch means actuable to cut oiT the current to said conductor in response to movement of said operative member, a container having an aperture in the bottom thereof mounted to the end of said operative member whereby a stream of coolant being discharged from said conductor is directed into said container, said switch means having resilient means whereby it is biased into an actuated position to cut off the current to said conductor, the weight of said container when partially full of coolant being sufl-lcient to depress said operative member and de-activate said switch means, said aperture allowing escape of coolant from said container whereby when the rate of flow of said stream drops and remains below that which is necessary to cool said conductor, said container progressively lightens to the point where said resilient means overcomes the weight of said container and said switch means is activated to cut olf the current to said conductor.

References Cited in the file of this patent UNITED STATES PATENTS 1,708,235 Nu'gent Apr. 9, 1929 2,325,638 Strickland Aug. 3, 1943 2,408,350 Strickland Sept. 24, 1946 2,572,073 Strickland et al. Oct. 23, 1951 2,786,418 Peck Mar. 26, 1957 

1. AN ELECTRICAL INDUCTION HEATING FURNACE COMPRISING A CONTINUOUS, HELICALLY WOUND, HOLLOW CONDUCTOR, A FLUID COOLANT FLOWING THROUGH SAID CONDUCTOR AND BEING DISCHARGED THEREFROM INTO AN OPEN DRAIN, SWITCH MEANS MOUNTED ADJACENT SAID DRAIN AND HAVING AN OPERATIVE MEMBER PROJECTING OVER SAID DRAIN, SAID SWITCH MEANS ACTUABLE TO CUT OFF THE CURRENT TO SAID FURNACE IN RESPONSE TO MOVEMENT OF SAID OPERATIVE MEMBER, A CONTAINER HAVING AN APERTURE IN THE BOTTOM THEREOF MOUNTED TO THE END OF SAID OPERATIVE MEMBER WHEREBY A STREAM OF COOLANT BEING DISCHARGED FROM SAID CONDUCTOR IS DIRECTED INTO SAID CONTAINER, SAID SWITCH MEANS HAVING RESILIENT MEANS WHEREBY IT IS BIASED INTO AN ACTUATED POSITION TO CUT OFF THE CURRENT TO SAID FURNACE, THE WEIGHT OF SAID CONTAINER WHEN PARTIALLY FULL OF COOLANT BEING SUFFICIENT TO DEPRESS SAID OPERATIVE MEMBER AND DEACTIVATE SAID SWITCH MEANS, SAID APERTURE ALLOWING ESCAPE OF COOLANT FROM SAID CONTAINER WHEREBY WHEN THE RATE OF FLOW OF SAID STREAM DROPS AND REMAINS BELOW THAT WHICH IS NECESSARY TO COOL SAID FURNACE, SAID CONTAINER PROGRESSIVELY LIGHTENS TO THE 